Through supervision system



' May 18, 1943 H w, UL ICH 2,319,358.

FIG. 7

THROUGH SUPERVISION SYSTEM Filled Oct. 7, 1941 3.Sheets-Sheet 1 b "F r n L| i m INVENTOR b! n. ULRICH ATTOkA/E'V y 19-43 H. w. ULRICH 2,319,358

THROUGH SUPERVISION SYSTEM Filed Oct. '1, 1941 s Sheets-Sheet 2 INVENTOR h: n! ULRICH BK ATTORNEY y 1943 I H. w. ULRICH 2,319,358

I THROUGH SUPERVISION SYSTEM Filed Oct. 7, 1941 s Sheets-Sheet 5 OPERA TE ml/swim I By H.W.ULR/CH A TTORNEV Patented May 18, 1943 THROUGH SUPERVISION SYSTEM Horace W. Ulrich, Newark, N. J assignor to liell Telephone Laboratories, Incorporated, New York, N. Y'., a corporation of New York Application October 7, 1941, Serial No. 413,933

6 Claims. (Cl. 179-41) This invention relates to telephone systems and more particularly to improvements in cord and trunk circuits for interconnecting a telephone subscriber in a local or tributary exchange with a toll office.

An object of the invention is to provide through supervision of the trunk from the subscriber to the toll; operator regardless of the direction of the, call A feature of the invention resides in such an arrangement of the trunk and local exchange cord circuit that when the toll operator is connected to one end of the trunk and the subscriber to the other through the medium of the local exchange cord circuit, the subscribers' switchhook will control supervision through to the toll operator.

More specifically the arrangement of the cord and trunk circuit is such that when the subscriber is connected to the trunk and the receiver is on the hook, a balanced Wheatstone bridge circuit is established, including the sleeve circuit of the cord and trunk, which bridge is unbalanced to operate supervisory control means in the trunk when the subscribers receiver is removed from the hook. The invention will be understood from the following description and accompanying drawings:

Fig. 1 of which illustrates a common battery subscribers line adapted to be connected to by a cord circuit S at. a local exchange.

Fig. 2 shows the local exchange end of a twoway trunk line T extending to a. toll ofiice.

Fig. 3 shows the toll oilice end of trunk T; and

Fig. 4 is a schematic diagram showing a Wheatstone bridge circuit established when the cord SC is connected to the trunk T and befor the subscribers receiver is removed from the hook.

The operation ofthe circuit of the invention will now be described. First, it will be assumed that a toll operator at the distant toll office (Fig. 3)" desiring to be connected with subscriber A in the local exchange (Fig. 1) has inserted a plug I ofia toll cord, not shown, in the outgoing jack 2, of a trunk extending to the local ex-- change, whereupon sleeve relay 3 in the trunk operated from battery, not shown, on the sleeve of plug I, in an obvious circuit. Relay 3 in operating prepares a locking circuit for relay 4. When lug I is fully inserted in jack 2, battery, not shown, connected to the ring of plug I causes relay 4 to operate over its contact 5. Relay 4 operated closes a circuit to operate reversing relay 6 which circuit can be traced from battery,

winding of relay 6, contact I of relay 8, and uppermost contact of relay 4 to ground. Relay 4 also locks over its contact 9, and the contacts of relay 3, to battery in series with a resistance. Operation of relay 4 removes its winding from the ring conductor of the trunk. Operation of relay 6 reverses battery and ground over the trunk, thus causing operation of polarized relay I0 at the local exchange in a well-lmown manner. Operation of relay 6 also closes a circuit to operate relay II which in turn operates relay I2, and further, at its contact I3, closes a circuit from ground at the back contact of relay. I4 to operate relay I5 which relay in operating opens at its upper contacts, the bridge, including retard coil I6 across the trunk, thereby l hting the supervisory lamp, not shown, oi t e associated cord circuit at the toll office. Operation of relay I 2 connects battery at its lowermost contacts to light the busy lamps I8, I9 and associated with the multiple jack appearances of the trunk.

Operation of relay l0 at, the local exchange causes relay 2I to operate, which at its contacts 22 closes a circuit for relay 23 to light the busy lamps such as 24, lights the line lamp 25 in a circuit including contacts 26 of relay 2I and contact 21' of relay 28 and, at contacts 29, closes one point in a supervisory bridge which will be completed at contacts 30 of relay 3| when that relay operates.

When the local operator answers the call by inserting the answering plug 32 of cord circuit SC in jack 33, trunl; sleeve relay 34 operates in series with cord supervisory relay 35 which latter relay also operates. Relay 34 closes its lower contacts thereby connecting battery in series with resistance 36 to the winding of polarized relay 31 and closes its upper contact," thereby connecting ground to the winding of relay 3| which relay operates to close its contacts 44 as soon as plug 32 is fully inserted in jack 33, the circuit for which can be traced from the cord circuit battery B, lower right winding of cord circuit repeating coil 38, winding of answering supervisory relay 39, ring contacts of the plu and jack, lower left winding of repeating coil 40, conductors 4| and 42, contacts 43 and winding of relay 3I to ground over the upper closed contacts of relay 34. Closure of contacts 44 of relay 3| connects battery to its winding thereby causing complete operation of this relay to close its contacts45 which completes a circuit to operate relay 28, to open its contacts 43 to disconnect its windings from the ring of the trunk,

and by closing its contacts to complete the closure of the supervisory bridge, whereupon cord supervisory relay 39 operates to remove ground at its back contact from the supervisory lamp 46. Operation of relay 28 locks over its contacts 41 to grounded contacts 48 of relay 2| and opens its contacts 21 to extinguish the line lamp 25.

The local operator after ascertaining the number of the wanted subscriber by well-known means, not shown, inserts calling plug 49 in the jack of the called line, whereupon the subscriber is rung in a well-known manner by means not shown.

When plug 49 is inserted in the jack of the It will be noted that when the operator inserts plug 32 in jack 33, a sleeve circuit was completed from battery, winding of cord sleeve relay and winding of trunk sleeve relay 34 to ground in series with a resistance 52. With truck sleeve relay 34 operated in this circuit, a Wheatstone bridge circuit is established as shown schematically in Fig. 4 in which one arm comprises the winding of sleeve relays 35 and 34, the second arm includes resistance 52, a third arm includes resistance 53, the fourth arm includes resistance 36, the winding of relay 31 is connected between the junction point of arms I and 2 and 3 and 4, and battery is connected between the junction points of arms I and 4 and 2 and 3. The resista-nces 52, 53 and 36 and the windings of relays 34 and 35 are so chosen that under the conditions existing prior to answer of the called subscriber, the bridge is in a balanced condition and a zero potential exists across the winding of relay 31 which therefore remains unoperated.

When the called subscriber answers, however, supervisory relay 54 operates thereby opening its back contacts to extinguish the supervisory lamp 5| and connects ground, at its front contacts,-

to operate relay 55 which relay in operating connects a resistance 56 in shunt to the Winding of relay 35 thereby lowering the resistance of the first arm of the Wheatstone bridge circuit and upsetting its balance, whereupon relay 31, which is of a, sensitive type, operates, thus completing a circuit for operating relay 51 which can be traced from battery, lower winding of relay 51 and contacts of relay 31 to ground at contacts 45 of relay 3|. Operation of relay 51 short-circuits the lower (high resistance) winding of relay In which circuit can be traced from the upper terminal of the lower winding, contacts 58 of relay 51 and contacts 59 of relay 60 to the lower terminal.

This reduction in resistance of relay l9, which is 60 connected across the trunk to the toll ofiice, causes relay M at the toll ofiice to operate, thus removing ground from relay 5 which releases and connects retard coil l6 across the trunk to operate the toll operators supervisory relay and y extinguish the supervisory lamp.

When the called subscriber replaces his receiver, the supervisory relay 54 will release to relight the supervisory lamp 5| in the local cord and release relay 55 thereby restoring the Wheatstone bridge circuit to a balanced condition whereupon relay 31 will release in turn releasing relay 51 which removes the short circuit from the lower winding of relay Ill thus increasing its resistance across the trunk sufliciently to cause relay M at the toll oflice to release, thereby reoperating relay l5 and removing the bridge from across the trunk which causes the toll operators supervisory relay to release and the cord supervisory lamp to light as a signal to the operator that the called subscriber has hung up.

If the call is in an opposite direction, i. e., from subscriber A to the toll ofiice, the call will be answered by inserting plug32 of the cord circuit SC in the subscribers line jack and extended to the toll office by inserting the calling plug 49 in the jack 33 of the trunk T.

When the plug 49 is inserted in jack 33, thereby operating relays 59 and 34, 9, Wheatstone bridge circuit similar to the arrangement previously described and shown in Fig. 4 is established except that relay 39 replaces 54, relay 6| replaces 55, relay 50 replaces 35 and resistance 62 replaces resistance 56. If the subscriber remains on th line, i. e., his receiver is not replaced on the switchhook after giving the call to the operator, and if the operator does not disconnect his line by removing plug 32, the Wheatstone bridge circuit thus established will be unbalanced due to the fact that relay 6| is operated which connects resistance 62 in shunt to the winding of relay 53, thus causin relay 31 in the trunk to operate. When the plug 49 is fully seated in the trunk jack, battery B in the cord is connected over the lower left winding of repeating coil 38, winding of relay 54, ring contacts of the plug 49 and jack 33, lower left winding of trunk repeating coil 49, and conductors 4| and 42, contacts 45 and winding of relay 3|, to ground at the upper contacts of sleeve relay 34. Relay 3| partially operates in this circuit to close its contacts 44 whereupon this relay fully operates and locks under control of relay 34.

Relay 3| in operating closes a circuit to operate relay 28 which opens the circuit of line lamp 25. Relay 3| also opens its contacts 43 to disconnect its winding from the ring of the trunk, closes at its contacts 30 one point in the supervisory bridge and at contacts 45 connects ground to a contact of relay 31.

Under the assumed condition, i. e., subscribers receiver oiT the hook, relay 31 is operated and therefore a circuit is closed to operate relay 51 which can be traced from ground, contacts 45 of relay 3 I, contacts of relay 31 and lower winding of relay 51 to battery. Until the toll operator answers, a parallel circuit, independent of relay 31, is also closed to operate 51 Which can be traced from ground, contact 63 of relay 64, contacts 65 of relay 3|, contacts 66 of relay 2| and lower winding of relay 51 to battery. Operation of relay 51 closes its contacts 58 thereby placing a short-circuit around thelower (high resistance) winding of relay |0, thereby operating relay I4 in the trunk at the toll ofiice to operate relays 61 and 68. Relay 61 operates relay l2 which opens at its upper contacts the energizing circuit for relay 38 which releases thereby completing a circuit to light the trunk lamp 69.

When the toll operator answers, relays 3, 4 and 3 operate. Relay 6 reverses the battery over the trunk thereby operating relay I!) which operates relay 2| to close its contacts 29 thereby completing the supervisory bridge to cause relay 54 in the cord to operate to extinguish the cord supervisory lamp 5|. Operation of relay 2| opens its contacts 66 thereby opening the previously mentioned parallel circuit for relay 51 and closes its contacts 48 to provide a locking ground for relay 28. Busy relay 23 operated to light the busy lamp whenrelay 3|: operated; The short-circuit around the lower winding of relay l isnow maintained under control of the calling subscribers switchhook thus holding relay |4 operated in an obvious manner which will be understood from the preceding description. 1

When the calling subscriber replaces his receiver on the hook, thus balancing the Wheatstone bridge, relay 31 will release thereby releasing relay 51 to cause relay l4 at the toll office to release and light the toll cord supervisory lamp.

In case the local operator inserts plug 49 in the trunk jack 33, before connecting to the subscribers line, or if the subscribers line has been connected and the subscriber has hung up, relay 31' will not be operated, but relay 51 will operate as soon as relay 3| operates, as before, due to the closure of that relays contact 65. When the toll operator answers the call and relay I0 operates, relay 2| operates thereby opening its contacts 66 whereupon relay 51 releases thereby causing relay M at the toll ofiice to release to operate relay I5 and light the cord supervisory lamp.

Selective signaling to inward toll operator by means of plug supervision jack It will be noted that, on calls from the local exchange to toll, if the plug 49 of the cord circuit isinserted in through supervisionjack 33, the line lamp 69 at the toll office is lighted, which lamp, and its corresponding answering jack 18, is located at a so-called through operators position at which position calls for points served by others and distant toll operators are handled. At this through position facilities are provided for accurately timing such calls. The usual method being for the details of the call to be entered on a so-called ticket which is stamped by means of a calculagraph to indicate the startand finish of the conversation.

There are other cases, however, where calls from. the local exchange are for subscribers located in the area served by the first toll center which calls are charged by the local operator, as for example, by the collection of a coin deposited by the subscriber in a coirrbox. In the case of calls of this character, it is desirable, and the usual practice, for such calls to be handled at the toll office at a different operators position, as for example at a so-called "inward position of the toll board or at a'local A board position at which no facilities are provided for timing calls, the only function of the operator being to establish a requested connection leaving the matter of charging the calling subscriber to the originatingoperator at the local exchange.

In order to enable the local operator to selectively route calls over the trunk T to the proper operator, the trunk is provided, in addition to the previously mentioned through supervision jack 33 with a second jack 1| which for convenience is termed a plug supervision jack.

If the local operator desires to extend a call to an inward toll operator, she will insert plug 49 of her'cord circuit in jack 1| thereby operating sleeve relay 12 which in turn operates relay 64. Relay 64 in operatin prepares relay 3| for operation when the plug is fully inserted in the jack as previously described. Closure of contacts 13 of relay 3|, and contacts 14 of relay 64, complete a circuit including the upper winding of relay 51. This circuit can be traced from ground, contacts 13 of relay 3|, contacts 14 of relay 54, contacts 16 of relay 11, and upper winding of relay 51 to battery. Operation of relay 51 short-circuits, the high resistance windingof relay ID to cause line'relay' [4 from ground at contacts 13 of relay 3|, contacts ,14 of relay 64, contacts of relay 51, contacts 8| of relay 11 and winding of relay 60 to battery. Relay 60 in operating opens its contacts 59 thereby opening the high resistance (lower) winding of relay I'll. Relay 60 also opens its contacts 15 to open one parallel path for relay 51. Relay 6!) further closes its contacts 82 thereby operating relay 11 which in operating opens its contacts 16 thereby opening the circuit for the upper winding of relay 51 which now releases to complete disconnection of relay ID from the trunk to the toll oilice, thus releasing the line relay M at that point. Relay 11 in operating opens its contacts 8| thereby releasing relay 66 which is slow to release. When relay 60 is released, however, it recloses its contacts 59 and 15 and opens its contacts 82. Closure of contacts 59 recloses the circuit to connect the two windings of relay ID in series across the trunk and closure of contacts 15 reoperates relay 51 to short the lower (high resistance) winding of relay l0, thereby reoperating line relay I4 at the toll office. Relay 11 now remains operated due to a locking circuit for itself at its upper contacts thereby preventing a repetition of the foregoing sequence of operation and consequent continuous alternate release and operation of relay 51.

From the foregoing it will be noted that when plug 49 was inserted in jack 1|, line relay H at the toll ofiice was momentarily operated, released,

and immediately reoperated and thereafter held in an operated position as long as the plug is maintained in the jack.

On the first operation of relay I4, relays 61 and 68 operate. The circuit for relay 51 being traced from ground on the front contact of relay l4, contacts 83 of relay conductor 84 and winding of relay 61 to battery and the circuit for relay 68 being traced over the same circuit from ground at relay l4, contact 83 of relay ll,

conductor 84, contacts 19 of relay l2, conductor 85 and winding of relay 68 to battery. Relay 68 is ultra fast to operate and slow to release whereas relay 61 is only normally fast to operate but also slow to release. Relay 68 operated closes its contacts 18 thereby connecting ground to its winding over conductor 84, contacts 19 of relay l2 and conductor 85, thus holding itself operated under control of relay l2. Relay 61 is also held by this sameground connected to conductor 84. When relay 61 operates, which occurs slightly later than relay 68, it closes its contacts 86 thereby operating relay |2 which opens its contacts 19 thus opening the circuit for relay 68 which is slow to release. By this time, however, relay I4 has released. Relay I4, however, operates again almost immediately and relay 61 is reenergized again and held operated as long as plug 48 is maintained in jack 1|.

' The timing is such that relay |4 releases before 68 releases and therefore the release of relay l4 with 68 operated, causes relay 81 to operate, which opens the circuit of through lamp 69 and closes its contact 88 to light lamp 89 at the inward board in a circuit from battery, contacts 90 of relay 61, contacts 9| of relay ll, contacts 88 of relay 81, to lamp 89. Relay 81 in operating closes its contacts 92 thereby completing a locking circuit for itself under control of relay 61.

- It will therefore be understoodthatif the operator inserts plug 49 in jackll, lamp 89 will be lighted instead of lamp 69 as in the case when the plug was inserted in jack 33.

What is claimed is: I

1. In a telephone system, a first operator's position, a subscribers station l-ine terminating thereat, a trunk line also terminating at said first position, a cord circuit at said first position for interconnecting said line and trunk, a supervisory relay in said cord circuit controlled over said subscribers line, a second operators position terminating the other end of said trunk, means in said trunk at the first position for transmitting supervisory signals over said trunk to the second position, sleeve relays in said cord and trunk at said first position, a Wheatstone bridge circuit for controlling transmission of said supervisory signals over said trunk established when said cord circuit is connected to said trunk, said bridge including said cord and trunk sleeve relay, and means controlled by said cord supervisory relay for altering the balance of said bridge to control transmission of said supervisory signal.

2. In a telephone system, a subscribers station and line, a trunk line, a link circuit for connecting said line and trunk, and means controlled by the subscriber for transmitting supervisory signals over said trunk, said means comprising a Wheatstone bridge circuit established when said link circuit is connected to said trunk and maintained in a balanced condition until the subscribers station receiver is removed from the switchhook.

3. Ina telephone system, a subscribers station and line, a trunk line, a link circuit for connecting said line and trunk, and means controlled by the subscriber for transmitting the supervisory signals over said trunk, said means comprising a Wheatstone bridge circuit established when said link circuit is connected to the trunk in which one arm thereof includes the sleeve relays of said trunk and the corresponding sleeve relay of the link, and the other three arms include such resistance values that the bridge is in substantial balance until the other end of the link is connected to the subscribers line and the subscribers station receiver is removed from the hook.

"4.In a telephone system, a subscribers station and line,'a trunk line, a link circuit for connecting said line and trunk, andmeans in said trunk for transmitting supervisory signals thereover,

- said means comprising a relay connected in bridge between the junction of the first and second and third and fourth arms of a Wheatstone bridge established responsive to connection of said link circuit to said trunk in which the sleeve relay of the link and trunk form the first arm of the bridge, the second and third arms are of predetermined equal resistance and the resistance of the fourth arm is equal to the resistance of the first arm, whereby the potential across said bridge relay is substantially zero, and means controlled by the subscribers switchhook for changing the resistance of the first arm of the bridge to cause operation of said bridge relay.

5. In a telephone system, a subscribers station and line, a trunk line, a link circuit for connecting said line and trunk, and means responsive to actuation of said subscribers station switchhook for transmitting a supervisory signal over said trunk, said means comprising a Wheatstone bridge circuit established when said link is connected to the trunk.

6. In a telephone system, a first operators position, a subscribers station line terminating thereat, a trunk line also terminating at said position, a cord circuit at said position for interconnecting said line and trunk, a supervisory relay in said first position cord and controlled over said subscribers line, a second operators position terminating the other end of said trunk, a cord circuit in said second position adapted to be connected to the trunk, means in said trunk for transmittingsignals thereover, supervisory means in said second cord controlled by said trunk means, a sleeve circuit including a sleeve relay in said first cord operated when said cord is connected to the trunk, and means in said first cord controlled by the subscribers supervisory relay for controlling said trunk means over the sleeve circuit of said cord without releasing said sleeve relay.

HORACE W. ULRICH. 

